Feature request - add setting to disallow single-number cages

[Kiwaiti]

I think inclusion of cages with only a single square/number (and no operator, just displaying the number required) is a matter of preference and should be handled as such by including a setting to disallow them.
On further thought,

1. this could be expanded to set the number of CAGE_1 cages (currently set to half the number of different numbers available (this.mGridSize/2) on line 182 of GridView.java) on a sliding scale, BUT
2. since this is a modification of difficulty for grids of a given size, it should be reflected in Statistics somehow, and I have no idea how to go about that.